Weather is an obvious factor when determining the right time to start planting. Even after you get seed in the ground, growers have to be cautious of the potential effects cold temperatures have on their crop, especially its viability after a certain growing point. Here are a few things to consider before planting early.
Newly Planted corn
Corn imbibes 50 percent of the water necessary for germination within three hours of planting, assuming there is adequate soil moisture for this to happen. This is the most susceptible time for newly planted corn because imbibing cold moisture can severely disrupt the germination process and cause serious issues in the developing embryo.
Typically, within three days after planting, no more moisture is being taken up by the seed and the germination process is well underway. At this point, injury can occur but is rarely fatal and rarely causes effects on yield. The exception would be if temperatures drop below 28 degrees Fahrenheit at the growing point. I recommend checking this temperature in the morning, prior to the sun hitting the soil. Remember, at the VE–V5 stages, the growing point will be three-fourths to one inch below the soil surface.
Emerged Corn
Corn that is emerged and at the VE–V5 growing point remains protected below the soil surface where there is an insulating factor against cold temps. The liquids within the corn plant act as an antifreeze and keep the tissue from freezing at the 28 degrees Fahrenheit mark. For temps below this, it is possible to see some frost damage on the leaf margins and tissue. However, this is rarely fatal or affects yield. The exception again would be the growing point and the temperature at the growing point.
Newly Planted Soybeans
Unlike corn, soybeans are not subject to imbibitional chilling. This does not mean that soybeans are immune to cold weather and rain; it simply means that they will not suffer germination and growth and development issues if they are subjected to cold temperatures and moisture. Soybeans are the ideal candidate for planting in questionable weather patterns.
Emerged Soybeans
Emerged soybeans can be injured by temperatures below 32 degrees Fahrenheit. However, the factors involved in determining the extent of the damage are row width, duration of cold temperatures and growth stage of emerged soybeans.
Narrow-row, drilled soybeans tend to hold in more ground warmth if soil temperatures have risen above 40 degrees Fahrenheit. This thicker canopy has the ability to hold in the radiant heat of the sun. However, as most soybeans either lie dormant waiting for moisture and temperature to germinate or will just have emerged, this benefit is not likely. Temperatures between 28–32 degrees Fahrenheit for short periods of time will not have a deleterious effect on young soybean plants; however, long periods in this temp range will have killing effects on emerged plants.
A little rain (or snow) that coats the plant or ground will also act as an insulator. Much like citrus growers who water lightly before a freeze and let the ice “insulate” the fruits or blossoms, the moisture can act in the same way.
Where do growers go from here? Patience is key! While soil conditions are better than we have seen in some areas in more than a year, an early rush to plant is not always warranted. Careful consideration should be given to the risk as well as the reward of early planting. For more information, contact your local Stine representative or your Stine regional agronomist for help.